Mechanical Ventilation with Heat Recovery (MVHR)

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Mechanical Ventilation with Heat Recovery (MVHR)

What is an MVHR System And How Does It Work?

Mechanical Ventilation with Heat Recovery (MVHR) is a ventilation system that comprises of a suitably sized heat recovery unit and a network of ducting connected to each room, used to remove moisture and stale air from your property, whilst at the same time introducing fresh, clean and filtered air back into your home via a heat exchange unit.
Mechanical Ventilation with Heat Recovery (MVHR)This works from a single unit most often located inside the building, most often a loft space and it works by continuously extracting air from the wet rooms of the property (bathrooms, kitchens, ensuites, utility etc, whilst at the same time drawing a fresh supply of air from the outside.

The heat is recovered from the extracted stale air via a heat exchanger in the unit and then is re-used to temper the clean, fresh filtered air supply for the other rooms such as living rooms and bedrooms etc.
Up to 95% of the heat can be recovered. The heat recovery unit runs continuously and can be boosted with most systems, some automatically with applicable models, when higher rates of ventilation / extraction are required such as when bathing or cooking.

The MVHR systems have “Summer By-Pass” functions of which are activated where the property continues to be ventilated and receive the expected fresh, clean filtered air, however the heat recovery process is intermittently switched off meaning that the heat recovery is bypassed.

What are the benefits of having Heat Recovery Ventilation?

What are the benefits of having Heat Recovery Ventilation?Heat recovery ventilation systems and their desire for installation into new homes have become more and more popular over the past few years especially as improvements with airtightness through Building regulations have increased. Besides making the dwelling more efficient and driving the moisture out, other reasons which may make you consider the installation of an MVHR could be:

Air Quality – If the dwelling has issues with air quality, eg for people who suffer from hay fever, the various kinds of filtration in the MVHR systems can deal with pollen, as well as rural & industrial smells including radon. The position of the air intake can be decided in order to avoid as much polluted air from nearby roadways.

High levels of humidity is dealt with by the constant ventilation as well as the system itself actively dehumidifying when it colder outside than inside.

Your Comfort – In areas where there are those annoying midges flying around, the MVHR system with tight-fitting filters helps to keep the dwelling free from these little annoyances.

Low Noise & Non-Intrusive ventilation system.

A few common questions answered

At what stage of the building process should the MVHR system be designed for my dwelling?
At what stage of the building process should the MVHR system be designed for my dwelling?As early as possible is the simple answer. As soon as planning has been permitted. We at SWES Ltd work closely with customers, builders and architects as early as possible to work out their specific needs and to overcome any possible issues during the design stage.

Can these be retrofitted – the answer is simply yes, however, due to accessibility and the fact that the dwelling is already complete, the process may be a little trickier for design, situ, duct runs, etc.

Can an MVHR be Installed in all types of properties?
Although MVHR can be installed in all types of buildings, we would only recommend it for buildings with very good airtightness levels. As a rule of thumb, this would be where the air permeability of the thermal envelope is at or below 3m3/m2.h @50 Pa. If this level of airtightness is not achieved then the heat recovery and consequent energy saving benefits of MVHR would be lost.

Running Costs
On average it costs between £15 to £40 per year in electricity to run an MVHR system constantly, but you will likely save some money on heating bills as the MVHR system will recover up to 90-95% of the heat that would normally be lost to leaks and draughts through the fabric of the building.
There are required periodic checks and the replacement of filters that are required often between 1 and 3 years.
There are various makes and models on the market these days which can accommodate all types and sizes of dwellings, however, we at SWES Ltd use MVHR Systems, designed and manufactured by Envirovent as our go to brand, although we can offer Nuaire & Vent Axia to name but a few.

There are many Frequently Asked Questions surrounding MVHR and other Ventilation Systems that can be found on our web page, so please explore more by clicking the following link.

Ventilation FAQs | Allergies | Ventilation Running Costs (

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